Adrenaline directly affects

Options

A. SA node
B. `beta-`cels of Langerhans
C. dorsal root of spinal nerve
D. epithelial cells of stomach.

Explanation

**Step-by-Step Solution:**

1. **Understanding Adrenaline**: Adrenaline, also known as epinephrine, is a hormone produced by the adrenal glands. It plays a crucial role in the body's response to stress or emergency situations.

2. **Function of Adrenaline**: Adrenaline is often referred to as the "emergency hormone" because it prepares the body for rapid action in response to perceived threats. This response is commonly known as the "fight or flight" response.

3. **Target of Adrenaline**: One of the primary targets of adrenaline is the sinoatrial (SA) node of the heart. The SA node is responsible for initiating the heartbeat and regulating heart rate.

4. **Effect on the Heart**: When adrenaline affects the SA node, it leads to an increase in heart rate. This increase in heart rate is essential for pumping more blood to the muscles and vital organs during stressful situations.

5. **Additional Effects**: Besides increasing heart rate, adrenaline also enhances breathing rate, raises blood pressure, and increases blood sugar levels. These changes collectively prepare the body for quick and efficient responses to emergencies.

6. **Conclusion**: Therefore, the direct effect of adrenaline is on the SA node, which increases the heart rate and prepares the body for emergency situations.

**Final Answer**: Adrenaline directly affects the sinoatrial (SA) node of the heart.

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